Field of the Invention
The present invention relates to a method of driving an organic light emitting display apparatus. More particularly, the invention relates to a method of driving an organic light emitting display apparatus including a panel where two organic light emitting diodes are provided in each of a plurality of pixels.
Discussion of the Related Art
As a type of flat panel display (FPD) apparatus, organic light emitting display apparatuses have a characteristic where luminance is high and an operating voltage is low. Also, since the organic light emitting display apparatuses are self-emitting apparatuses that self-emit light, the organic light emitting display apparatuses are high in contrast ratio, are implemented as ultra-thin display apparatuses, have a response time of several microseconds (p), and are not limited in viewing angle, thereby easily realizing a moving image. Also, the organic light emitting display apparatuses are stably driven even at a low temperature and are driven with a low voltage of direct current (DC) 5 V to 15 V, and thus are easily manufactured and designed.
Therefore, an organic light emitting display apparatus having the above-described features is being applied to televisions (TVs), monitors, various information technology (IT) devices such as mobile terminals, etc.
A basic structure of a plurality of pixels which are provided in a panel applied to an organic light emitting display apparatus is as follows.
Each of the pixels provided in the panel is configured with an array element and an organic light emitting diode (OLED).
The array element includes a switching thin film transistor (TFT), which is connected to a gate line and a data line, and at least one driving TFT connected to the OLED.
The OLED includes a first electrode connected to the driving TFT, an organic emission layer, and a second electrode.
In the pixels having such a configuration, the organic emission layer itself is formed of a plurality of emitting materials that respectively emit red, green, and blue, and thus, a full color is displayed. Also, the whole organic emission layer is formed of an organic emitting material that emits white, and thus, in a case where each of the pixels outputs white light, a color filter pattern including red, green, and blue pigments is provided in correspondence with each pixel. Therefore, white light emitted from the organic emission layer emitting the white light passes through red, green, and blue color filter patterns, and thus, a full color is displayed.
However, in a process (for example, a process of manufacturing a line, a switching TFT, and a driving TFT) of manufacturing a panel having the above-described configuration, a characteristic of a TFT is degraded, or internal short circuit occurs. For this reason, some pixels cannot normally be driven.
For example, when a TFT provided in one pixel is not normally driven, a current or a voltage is not applied to the OLED connected to the TFT, and thus, the one pixel is blackened.
Moreover, when a source electrode and a drain electrode of the driving TFT are short-circuited, the driving TFT is not normally driven, and a voltage applied to the source electrode is directly applied to the drain electrode, whereby a pixel is driven. In this case, the pixel is always turned on and thus is whitened.
When one pixel is blackened or whitened, a blackened area cannot be repaired due to a structural characteristic, and thus, a blackened state is maintained as-is.
Moreover, in a whitened area, an electrical connection between the driving TFT and the first electrode and an electrical connection between the driving TFT and the switching TFT are disconnected through laser cutting. Furthermore, the OLED of a pixel which is whitened is welded, and thus, the first electrode is electrically connected to the second electrode, whereby the pixel is blackened.
Since a whitening defect is seen with a user's eyes due to good visibility, the whitening defect becomes a cause of degrading display quality. For this reason, even when the whitening defect occurs in only a portion of a whole display area, a display apparatus is defective and thus cannot be determined as a finally finished product.
However, a user can hardly recognize a darkened pixel, and thus, even when about 10 to 20 pixels are darkened in the whole display area, a display apparatus is determined as a finally finished product.
Recently, products having a high resolution of full-high definition (FHD) or ultra-high definition (UHD) and high display quality are released, and the demands of consumers for display apparatuses are enhanced. Therefore, zero-defect products which do not include an abnormally driven pixel at all are being required, or products where the number of darkened pixels is five or less are being required.
Therefore, manufacturers of organic light emitting display apparatuses desire to satisfy the demands of consumers, but due to a structural characteristic of the organic light emitting display apparatuses, there is no method of repairing a darkened pixel to a normal pixel. Also, a display area of an organic light emitting display apparatus includes tens to tens of millions of pixels, the manufacturing cost highly increases for manufacturing an organic light emitting display apparatus in order for a defect not to occur in all pixels.